engleski

Influence of the radiometric features of VNIR and TIR images on the automated detection and interpretation of objects

The main issue of the work was the measurement of the response of particular channels of the VNIR high resolution camera aimed for the development of the radiometric calibration. The analysed VNIR camera has several controlable parameters: gain, integration (exposition) time, bias, separately for near infrared (NIR) and red (R), channels and common for green and blue (G/B) channels. The control of these parameters is possible during the airborne acquisition and this provides very flexible imaging system that can be matched to the actual visibility above the mapped terrain. The measurements show that the channels of the VNIR camera have very different responses in NIR and R channels in comparison to G/B channels, if the gain was changed from minimum to maximum. The particulary powerfull feature of the considered digital VNIR camera is the available dynamic range, it can be 8 bits (from one to all four channels) or 10 bits (from one to three channels). Preliminary measurements and analysis show that 10 bits range enables robust mode of imaging during the changeable visibilty. The price for this is increase of the requirment to the memory of the acquisition system. The selection of the imaging parameters is not strightforward, it depends strongly on the features of the mapped scene. Recent analysis was performed with aim to enable production of the mosaics in visible (V) or in colour and the infrared bands (CIR). These mosaics serve as background for the subjective in-terpreetation of the shown scene, while outputs were landuse thematic map in CORINE methodology and specific features (vectors). Due to radiometric imperfection of the considered VNIR camera, the obtained VNIR images are radiometricaly distorted. The analysis of the influ-ence of the radiometric features of acquired images was performed on raw and on calibrated images, by analysis of the quality of the classification. The obtained results enable conclusion that the well calibrated digital VNIR camera can provide automated detection of objects in the scene and their thematic interpretation that was not possible on panchromatic digital ortho photo image map.

response; radiometry; radiometric calibration; classification; dynamic range

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